This is a review, listening tests and measurements of the GR Research B24 AC cable. I purchased it from the company direct. It costs US $349 in the 4 foot section I purchased.
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As the British saying goes, the B24 "looks the part" with the thick cabling and such. But fails in actual construction. When I attempted to first plug in the male end, it took incredibly force to push the earth/ground pin in. It it hugely oversized. It got progressively a bit better after a few insertions but then started to develop some scratches. Heaven knows what damage it has done to my outlet. Worse part was that when I first plugged it in, it was not passing any electricity! I look and it appeared to be fully inserted. Turns out it was not. There is this "shield sleeve" that slides forward pulling the heatshrink with it:
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So looking from outside, it seems the plug has completely mated with the outlet. But in reality, hot and neutral pins have yet to make a connection. You have to simultaneously pull back the sleeve while attempting to push the whole contraption forward. Given the large force you need to put in there, it takes some gymnastics to be sure. This whole affair has gotten worse due to ground pin being too long:
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Compared to my other AC cords, the ground pin is 1 to 2 mm is longer. This means that even though you feel like you have inserted the plug into the outlet, you have not yet. I can see this being done to support the crazy weight of these cables but come on. An cable should be easy to plug in and not remotely have such issues. So big fail on usability.
Company advertising says that you can try the cable out and if you don't like it, you can return it and "get your money back." Close look shows that you are responsible for shipping it back, the cost of shipping it to you and unknown credit card charges. I payed $40 for shipping for 2-day service ($25 for standard ground). So if I ship it back the same way, I will likely incur some $80. For this much money, could have bought a dozen ordinary AC cables. So much for money back guarantee.
And oh, those Velcro cables are mine in the picture. It doesn't come with any. I have bought cheap Chinese cables that came with set of Velcros.
Company makes two sets of AC cables, the B16 and B24 series. These are the number of wires that are put in the cable (or per line?). Strangely, despite its lower effective resistance, the B24 is said to be more suitable for sources/pre-amps than power amplifiers! So that is how I tested it.
GR Research B24 AC Cord Basic Measurements
I am going to do things differently than usual, starting with some simple measurements of the AC cord resistance and then jumping into listening tests, before showing more measurements. Here is the resistance of the cable as a whole and comparison to a few others I had on hand:
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The large number of parallel strands creates a very low resistance cable. Total resistance was just 0.005 ohm or 5 milliohm. For later tests, I pitted the B24 against the worst opposite which was a generic and thin AC cable. It naturally had much higher (relative) resistance of 81 milliohm per meter (compared to 4 for B24).
If you pulled the maximum allowed 15 amps allowed out of the typical US outlet, you would get a voltage drop of 1.8 volt with my longer thin AC cable vs 0.08 volt for the GR Research B24. The former is just 1.5% drop which is negligible. Still, at 0.1% drop, the GR Research B24 clearly has lower resistance. The edge though drops substantially when you compare it to much cheaper aftermarket cables from Pangea and
AudioQuest NRG-X3.
There are no regulator safety standards for the cable. The female IEC terminal has CE listing but the male end just says 15 amp/120 volt. Even if the latter was UL certified, the whole cable is not. So use it at your own risk!
GR Research B24 AC Cord Audio Tests
As a target, I used
Topping A90 Discrete pre-amplifier. It has built-in power supply so accepts an AC cord directly. Switching from one cable to the other took too long to allow valid listening tests. Sometimes one cable would sound better. Sometimes the other. Sometimes they would sound the same.
Since you can't hear what I heard, I resorted to null testing. I used an RME ADI-2 Pro FS and looped its audio output through Topping A90 Discrete. Output of the A90D was then captured using RME's ADC. By using the same DAC and ADC, I removed clock variations, allowing for excellent nulling. Member
@pkane 's excellent DeltaWave software was used to perform the matching.
First test was a classical record (CD) of Vivaldi's Four Seasons conducted by Christopher Warren-Green of London Chamber Orchestra:
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The difference between output of the Topping A90D using generic thin AC cable and B24 was identical, resulting in just very low level noise at or below that of 16 bit CD content. Content is copyrighted but here is the difference file for you to listen to:
https://www.dropbox.com/s/1qftq2r8bkw84hw/AC Power Difference.wav?dl=0
Next I tested the track Hunted from one of my favorite bands, Radical Face and their Missing Film album:
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On average we null down to the same -94 dB levels. If you listen to the difference signal, at extreme amplification, you can barely here tiny regular noise pumping. This is an artifact of the matching I believe than any audible difference. You are welcome to perform an ABX test as I can share the files here due to kind permission from the band: [youtube comment]
"Missing Film" is a selection of instrumental music I've written and recorded over the past two years. These tracks range from film and TV commissions that didn't pan out, to one-off experiments that have no home. Instead of letting these just sit idly on harddrives, I thought I would make these tracks available to film makers to use, royalty-free, in any of their personal work. So as long as it's non-commercial, you can use any of these tracks for your work and do not need my explicit permission. "
I chose to purchase the album though through bandcamp and I suggest you do the same:
https://radicalface.bandcamp.com/album/missing-film
You can pay whatever you choose. Anyway, here are the clips and difference file:
Radical Face Hunted:
Generic AC Cable:
https://www.dropbox.com/s/gj74weg67t2bwkh/Radical Face Hunted Generic AC Cord.wav?dl=0
GR Research B24:
https://www.dropbox.com/s/7pft7ci37d4rbbj/Radical Face Hunted GR Research B24.wav?dl=0
Difference:
https://www.dropbox.com/s/tpg17rdfjr1g5co/Radical Face Hunted Difference.wav?dl=0
I grabbed another track,
I'll Be There Soon from same album which has different instrumentation:
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This one nulled nicely and all that is there is noise even if you turn up the gain some 60 dB.
Here are the tracks again: Radical Face: Missing Film - I'll be there soon
Generic AC Cable:
https://www.dropbox.com/s/v5dxg23j6rfeba3/Radical Face I'll be there soon Generic AC.wav?dl=0
GR Research B24:
https://www.dropbox.com/s/33l12ajgaiphe8m/Radical Face I'll be there soon GR Research B24 AC.wav?dl=0
Difference:
https://www.dropbox.com/s/ys5lva8w9bqghzl/Radical Face I'll be there soon Difference.wav?dl=0
Dropbox can play these files in place so you don't even need to download them. Just click on the links and play them in the new window.
Note that the tracks I picked above are some of my references for testing and enjoyment. They are superbly recorded and any difference in fidelity, should be obvious. There was none in my listening.
GR Research B24 Measurements
Company talks about how their cord "filters" other noise. Since your electronics performs strong filtering of its own, such a thing is not material. But for grins, I tested the worst case of treating the AC cable as an interconnect and putting a powered transformer right next to the cable:
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The GR research B24 is indeed less receptive to AC noise inducement. As shown though in green line, even if you used any of these AC cord as an audio interconnect, their noise still be inaudible!!! Of course, when used as a power cord, such induction will be beneficial as you would get tiny amount of extra power for free.
We don't listen to power cables directly though so let's plug them into Topping A90 Discrete again and see if its performance changes. Let's start with frequency response to detect tonality changes:
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None is there. While not shown, the result was the same with the other two power cords mentioned early in the review. I next ran our dashboard:
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As expected, there is no change whatsoever. Performance is superb whether I use a cheap generic cable or B24. Before someone complains above is at one frequency, let's test at many and include ultrasonics in there as well:
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There is not even a hair difference. Noise+distortion is below threshold of hearing even though we measure it out to 90 kHz.
Finally as a simulate of "music," let's test with 32 tones:
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There is not even a slightest difference anywhere in any part of the spectrum with respect to noise or distortion.
I should say that my environment is quite "dirty." I have a workstation running these tests, an Audio Precision analyzer "polluting" the AC with its switching power supply. Half a dozen other devices from network switch to monitor and LED lamp is plugged in. An unterminated scope probe would show ton of airborne "interference" yet none is remotely impacting our audio device. Your situation in an audio system devoid of all the complexity of my system will be far less of a stress test.
Conclusions
We can naturally demonstrate through measurements that a monster heavy cable comprised of 24 individual cables does have lower resistance. And the weave is more resistance to AC noise pick up. As I keep saying though, we don't listen to AC cables, we listen to audio systems. Objective capture and nulling of the output shows zero difference brought to the table by the B24 cable. I have show three tracks. I am confident I can show you any number you want. Result will be the same. Sighted listening can yield "differences" but that can point to generic cable being "better" as well as the B24 depending on order, mood, amount of concentration, etc.
Blind test will show no difference because we know objectively there is no difference (because of the null).
Of course as usual, our measurements of the output of the device show identical performance as well. In the past, I have pumped heavily distorted AC waveform into audio devices with no impact on them whatsoever. What hope is there that any "filtering" of an AC cable will make any difference? It can't and it won't.
Beyond lack of improvement on fidelity of the system, I am super disappointed by the build of this cable. It is just awful and I am not talking about the massive weight and stress it puts on your equipment and wall outlet. But rather the poor build of the male plug that works so hard against you being able to perform the simple test of just plugging it in! In that regard, I put any of the brand name AC cable products way, way ahead of GR Research work here. This is poorly done hobbyist work that has not stood the test of any independent evaluation.
While sadly a norm in aftermarket AC cables, the B24 lacks any safety testing. Who knows how safely they have stuff so many wires into its terminations. Who knows what happens if there is a short in your equipment and stress is put on this cable to trip your breaker.
Bottom line, I see no redeeming quality in GR Research B24 AC cable and so cannot recommend it.
Edit: video review posted as well:
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